Study on aerosol transport behavior related to fission product release in nuclear power plant accidents

In severe nuclear accident (SA), radioactive fission products scape into the containment vessel (CV) due to primary system failure and be released into the environment through failure sites in the CV and reactor building. Transport and deposition of radioactive aerosols during such events can have significant and wide-ranging consequences for environmental contamination. The purpose of this study is to develop an evaluation method for aerosol migration based on transport mechanism at CV penetrations and failure locations during SA. An experimental setup has been established, and a series of experiments were conducted to measure the time-averaged decontamination factor (DF). Experimental parameters for DF measurements included flow rate, channel diameter, channel length, particle size, and measurement time. A theoretical transient aerosol transport model was developed that accounts for deposition and re-entrainment effects, with a particular focus on a horizontal circular pipe in turbulent flow conditions. This model accounts for position- and time-dependent concentration and deposited particle number on the surface, enabling the prediction of transient DF along with time-averaged DF for individual particle diameters. The developed aerosol transport model was validated by comparison with experimentally measured DF data. Finally, the sensitivity of the model and the effects of various parameters are discussed.